Estimation of thoron inhalation dose using a sensitive whole-body counter

Exposure to thoron daughters is a potential inhalation hazard in thorium handling facilities. The internal exposure of individual workers is estimated using air-sampling data and occupancy factor. In order to corroborate the results of this indirect method, a study was carried out by planned exposure of human volunteers to thoron daughters and in vivo activity measurements using a sensitive whole-body counter. The methodology and findings of such a procedure are presented in this paper. The effective dose equivalents estimated from the air sampling data and whole-body counting show agreement within ± 20%. (author)